The fatal stabbing of 70-year-old Margaret Krukowski on a train car filled with Christmas shoppers propels British author Cleeves’s excellent sixth mystery featuring Northumbrian Det. Insp. Vera Stanhope (after 2012’s The Glass Room). While some members of Vera’s team deal with the difficult task of identifying possible witnesses and suspects aboard the train, she and Sgt. Joe Ashworth, her protégé, begin the task of learning more about the victim, who lived in the seaside village of Mardle. The secretive Margaret resided at the Harbour Guest House, where she was almost part of owner Kate Dewar’s family. Cleeves expertly handles the interplay among Vera—outsized both in stature and personality—her staff, and the villagers. In addition to the series’s compelling regulars, the cast includes such brilliantly realized minor characters as Kate and Jane Cameron, who runs the Haven, a hostel for homeless women. You don’t have to be a fan of the TV show Vera, now filming its fifth season, to enjoy this top-notch police procedural. Agent: Moses Cardona, Inkwell Management. (Dec.)